In a study that prompted sharp criticism from other experts, French scientists said on Wednesday that rats fed on Monsanto's genetically modified corn or exposed to its top-selling weedkiller suffered tumors and multiple organ damage.
The French government asked the country's health watchdog to investigate the findings further, although a number of scientists questioned the study's basic methods and Monsanto said it felt confident its products had been proven safe.
Gilles-Eric Seralini of the University of Caen and colleagues said rats fed on a diet containing NK603 - a seed variety made tolerant to dousings of Monsanto's Roundup weedkiller - or given water with Roundup at levels permitted in the United States, died earlier than those on a standard diet.